Certain electronic components, for example power transistors, consume significant power in use. As a result, excess heat is generated which must be dissipated to prevent the component from overheating and causing damage thereto. Typically, heat sinks are used to absorb and dissipate heat away from such components. Free standing heat sinks may be attached to the component. Alternatively, a heat sink may be co-located with the component on a circuit board, and brought together to provide physical contact. Typically, the face of a power device is applied to a heat sink to ensure there is good thermal contact between the heat sink and the power device. This can be achieved by, for example, screwing (via a securing screw), or clipping the component to a heat sink located on the circuit board. Clipping provides better versatility with respect to assembly, and reduces the possibility of damaging the component if too much pressure is applied when screwing the component and heat sink together.
Certain components, such as power transistors, generally include three legs (referred to alternatively as “pins”) for electrical and physical connection to a printed circuit board (PCB). The free ends of the legs are typically soldered to the circuit board to secure the component thereto. Often, the ends of the three legs are arranged in a row (i.e. in the same plane) when attached to the PCB. However, it is preferable to have sufficient (electrical) clearance between the component legs. This can be achieved by arranging the central leg to be offset from the outer legs, so as to form a triangular footprint on the printed circuit board beneath the component. Generally, the legs exit the body of the component in the same plane (i.e. in a row), and, in order to provide the central leg to be offset, it is typically bent in a stepped form. This term “offset” can therefore be construed as, in relation to a leg, a leg whose distal (free) end is in a different plane to the other legs.
There are, however, problems with such designs. After such a component has been fixed onto a PCB, in order to secure the face of the component to a heat sink, a lateral force is applied to the component in a direction parallel to the circuit board (and substantially perpendicular to plane of the legs and the body of the component). Non-offset designs can flex somewhat; the component body offers a degree of flexibility and “give” when the component is in situ on the circuit board, and lateral forces are applied to the component body. However, component arrangements with an offset central leg are not resilient when such lateral pressure is applied to the device. In particularly, excessive compressional and tensional forces are formed in the central leg as a result.